Primary crystallization reactions in Al-based metallic glass alloys

For Al-based metallic glasses primary crystallization is effective in yielding nanoscale microstructures with crystal densities upto 1022 m−3 or higher. The crystallization kinetics determinations support a heterogeneous nucleation from quenched in atom arrangements that act as catalysts, but the kinetics are also influenced by transient effects. The decaying growth rate at long times can be related to diffusion field impingement, but other factors operate at short times. The primary crystallization reaction can be controlled effectively by suitable minor solute substitution to enhance nanocrystal densities upto 1023 m−3 at refined sizes or to inhibit nucleation to lower densities of about 1020 m−3. These developments offer new opportunities for control of nanoscale microstructures and also challenges for the understanding of the reaction mechanisms.